Transmission control circuit



P. R. THOMAS TRANSMISSION CONTROL cmcun" Filed Oct. 30, 1931 May l6, 1933.

INVENTOR P. R. THOMAS BY ATTORNFY Patented May 16, 1933 litres STATS y rec e PHILIP a. THOMAS, or .A'LDWYCH, LONDON,- ENGLAND, assienon 'ro wns'rnnn ,ELEG- TRIO COMPANY, INCORPORATED, YORK Application filed October 30, 1931, Serial No. 571,947, and in. Gre

. over of direction of transmission of telegraph I the signals are not clipped or abbreviated or even lost completely due to the time taken to perform the switching operations.

In accordance with the present invention there is provided in a cable system comprising speech and telegraph circuits where the direction of transmission of telegraph is under the control of the speech, means to delay the application of telegraph signals to any part of the system until such part is in a condition for transmission.

By way of illustration, one embodiment of the invention will be described with reference to the accompanying drawing which illustrates one terminal of a cable system.

Referring to the drawing it will be seen to represent one terminal of a cable in a receiving condition.

The cable terminates in a four-wire circuit in the usual manner comprising telephone branch L L telegraph branch TL TL and the filters F and F for separating tele phone and telegraph signals. In the telegraph branch there is shown the usual telegraph transmitting and telegraph receiving amplifiers designated TA and TA respectively and a telegraph transmitter T1. In the telephone branch are the usual amplifiers A and A and the additional apparatus designated D and AD with switches S S and S operated by the latter. D is a delay network designed to delay the speech in L for a period long enough to enable switches S S and S to operate in response to operation of the apparatus A13 which may be a vacuum tube amplifier-detector circuit such as is well known in the art, under control of the speech picked off from L in front of the delay network D, before the speech arrives at the switching point in L Suflicient apparatus TRANSMISSION CONTROL CIRCUIT at Britain December 23, 1930.

render clear the working of the .invention only has been shown audit willibe appreciated by those skilled in the art that other well known apparatus will be required to complete theterminal equipmen Assume now that speech arrives on the line L It will be amplified by amplifier A the output ofwhich will divide between delaynetworkD and amplifier detector AD The main portion of the speech passes through the delay network where ltstransit time; is appreciable, the network being designed accordingto known principles to produce a dc lay greater-than the time required by the switches :5 Sgand S to operate. Some of the. speech is diverted through amplifier detector All) the output of which operates the three switches S puts the telephone transor new Yoiair, n. Y., a. conrona rron on NEW mitting line L in connection with the cable I C and disconnects the telephone receiving line L therefrom, and S -puts the telegraph transmitting line TL in connection with the cable and disconnects the telegraph receiving line TL therefrom. The same speech also operates S which is a slow operate relay. This relay puts the telegraph transmitterTT in operation, but due to the fact that it has a greater time lag than the other relays the telegraph transmitter is not made operative until after the lineTL has been put in connection with the cable. It will be seen therefore that no loss of telegraph signals due to the change-over can occur.

The other terminal of the cable will be idenv tical with the one shown and :will of course be in condition to receive, that is, the corresponding switches will be in the positions shown in the drawing'tor S S and S When'speech originates from the other terminal the operation at that end Wlll'bG the same as described for the terminal illustrated.

In cable circuits having long transmission times, means may be provided to prevent the switches at both terminalsbeing s multaneously operated to the transmittmg posit ons...

These means may result in a long time de-.

laybetween the application of the speech to theamplifierdetector (A13 and its appli cation to the cable. During this'time delay a pulse ojtt'one' or other. signal may be transmitted over the cable, to disable the switchgear at the distant end and insure a free path for the following transmission. The operating time of the switch S is then made sufficiently long to cover the period thus required for insuring the proper operation of the switches controlling the direction of transmission over the cable circuit.

While only one method of carrying outthe invention is here described it will be apparent to those skilled in the art to make numerous modifications and to apply the invention to other systems of voice operated control of telegraph and it must be under: stood that the scope of the invention is defined in th'eappended claims.

What is claimed is:

- 1. A system for transmitting telephone and telegraph signals over a two-way signal transmission medium comprising at a terminal thereof a telephone transmitting circuit, a telegraph transmitting circuit normally disconnected from said medium and including a normally disabled telegraph transmitter, switching means responsive to initiation of telephone signals in said telephone transmitting circuit for connecting said telegraph transmitting circuit to said medium, and switching means also responsive to said telephone signals for conditioning said telegraph transmitter for operation subsequent to the connection of said telegraph transmitting circuit to said medium.

2. A. system for transmitting telephone and telegraph signals overa two-way transmission path comprising at a terminal thereof a telephone receiving circuit and a telegraph receiving circuit normally connect-ed to said path-so as to receive telephone and telegraph signals, respectively, therefrom, a telephone transmitting circuit and a. telegraph transmitting circuit normally disconnected from said path, said telegraph transmitting circuit including a normally disabled telegraph transmitter, switching means responsive to telephone signals initiated in said telephone transmitting circuit for disconnecting said telephone receiving clrcuit and saidtelegraph receiving circuit'from said path, and for 'connectlng said telephone transmitting c1rcuit and said telegraph transmitting circuit thereto, and slow operate switching means also responsive to the telephone signals initiated in said telephone transmitting circuit for conditioning said telegraph transmitter for operation.

3. A cable system for transmitting speech and telegraph signals over acable compris ing at a terminal thereof telephone and telegraph transmitting branches normally disconnected from the cable, a normally disabled 7 telegraph transmitter in said telegraph branch, switchingmeans responsive to the and telegraph branches to said cable, and

initiation of telephone signals in said etele i I phone branchfor connecting said telephone 

